Download The mystery of the evolution of stomata

Interviews with scientists:
The mystery of the evolution of stomata
Student Notes
Introduction and context
We take stomata for granted – they’re on every leaf around us, and without them the world
wouldn’t breathe. They don’t just respond to daylight and atmospheric humidity: new research
shows that plants slam their stomata shut against invading bacteria.
But when and how did this complex ability evolve? The fossil record leaves us with a fascinating
puzzle. In this 5 minute talk, Professor Alistair Hetherington of Bristol University discusses the
mysterious evolution of stomata.
Questions
1. Outline the mechanism of stomatal opening and closing.
2. Explain how the transpiration stream pulls water and minerals from the soil to the aerial
parts of the leaf.
3. Explain the importance of stomata to terrestrial plants.
4. Liverworts do not have stomata. How do their ‘leaves’ exchange gases with the
environment?
5. Draw out a phylogenetic tree for the following plant groups:
angiosperms, ferns, gymnosperms, hornworts, liverworts, lycophytes, mosses,
This web link may be useful http://intobiology.org.uk/stomata-key-elements-essential-forthe-succes-of-the-vascular-plants/
6. How old are the earliest known fossil stomata?
7. To which geological periods do Cooksonia fossils belong?
8. Between which groups on the phylogenetic tree of plants does Cooksonia sit?
9. What is known about the concentration of carbon dioxide in the atmosphere during the
Silurian period?
10. What is the evidence from the fossil record to support the hypothesis that stomata arose
only once during evolution?
Science & Plants for Schools: www.saps.org.uk
Interviews with scientists – the mystery of the evolution of stomata: p. 1